The typical application of a push-pull impeller is well known in HVAC application since 1935 (U.S. Pat. No. 1,672,272) and provide a mean of moving air in opposite direction with a single motor and to concentric cylinder. The anterior art is described in FIG. 1 and generally consists of a dual fan with inverted pitch blades located on the inside (1) and the outside (2) of a flow separation annulus (3).
In agrifood industry, heat, moisture and contaminants such as ammonium must be evacuated from production area to avoid performance lost. This problem is generally solved by high venting flow and high heating costs. Furthermore, most existing heat exchangers can't withstand the dust contaminant or ice formation. Clogging, moisture dripping or absence of good cleaning method compromise the use of heat exchanger in a northern climate.